Image-processing device with a first image sensor and a second image sensor

ABSTRACT

A first image sensor receiving light from a subject and a second image sensor capable of receiving light of the same image as the first image sensor and having a spectral sensitivity characteristic different from that of the first image sensor are provided. A color-correcting coefficient determining part calculates, based on each output value photoelectrically converted in the first and the second image sensors, a color-correcting coefficient with which a color-correcting part performs color correction on the output value of the first image sensor. Using the first and the second image sensors of different spectral sensitivity characteristics, parameters for receiving/recognizing light from a subject field can be easily increased to obtain a favorable color reproduction characteristic. Since applying the image-processing device to a conventional electronic camera including the first and second image sensors only requires a change in signal-processing method, it can be easily applied to an existing electronic camera.

This application is based upon the claims the benefit of priority fromthe prior Japanese Patent Application Nos. 2002-366298 and 2003-407514,each filed on Dec. 18, 2002 and Dec. 5, 2003, the entire contents ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image-processing device of a digitalcamera, a digital video camera, and the like.

2. Description of the Related Art

Conventionally, an image-processing device receives light of threeprimary colors R, G, and B and then photoelectrically converts thereceived light to perform color correction, thereby obtaining a desiredcolor reproduction characteristic.

In order to obtain a good color reproduction characteristic, such animage-processing device performs matrix transformation or look-up table(hereinafter, abbreviated as LUT) transformation for color correction(see Japanese Unexamined Patent Application Publication Nos. 2001-203903and 2002-10095).

In the above-described image-processing devices, however, there arises aproblem due to a difference in spectral sensitivity characteristicbetween the image sensor and the human eye that, for example, a certaincolor is recognized by the human eye but not by an image sensor.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an image-processingdevice that allows a favorable color reproduction characteristic to beobtained.

According to one aspect of the present invention, a first image sensorwhich receives light from a subject and a second image sensor capable ofreceiving light of the same image as the first image sensor and having aspectral sensitivity characteristic different from that of the firstimage sensor are provided in the image-processing device. Acolor-correcting coefficient is calculated by a color-correctingcoefficient determining part based on each output value obtained byphotoelectrical conversion in the first image sensor and the secondimage sensor. By using the calculated color-correcting coefficient, acolor-correcting part performs color correction on the output value ofthe first image sensor. By using the first and the second image sensorseach having a different spectral sensitivity characteristic in thismanner, parameters for receiving and recognizing the light from asubject field can be easily increased to obtain a favorable colorreproduction characteristic. In the case where the image-processingdevice is applied to a conventional electronic camera including thefirst and the second image sensors, only a change in thesignal-processing method is required. Therefore, the present inventioncan be easily applied to an existing electronic camera.

According to another aspect of the invention, the first image sensor isdivided into a plurality of small areas, and the second image sensor isdivided into a plurality of small areas so as to correspond to theplurality of small areas of the first image sensor. Then, the outputvalue of each pixel of the first image sensor and the second imagesensor is integrated for each of the small areas so as to calculate thecolor-correcting coefficient by using the integrated value. By dividingthe second image sensor into the plurality of small areas so as tocorrespond to the plurality of small areas of the first image sensor inthis manner, it is ensured that a favorable color reproductioncharacteristic can be easily obtained even when the first image sensorand the second image sensor have a different number of pixels.

According to a further aspect of the present invention, the first imagesensor and the second image sensor use a different number of pixels toreceive the light from the same subject. Therefore, the presentinvention is applicable regardless of the number of pixels of the firstimage sensor and the second image sensor.

According to a further aspect of the present invention, the second imagesensor is used as a colorimetric sensor which measures color balance ofthe subject. The exposure of the camera is controlled by an outputsignal from the colorimetric sensor.

According to a further aspect of the present invention, the second imagesensor is used as a photometric sensor which measures luminance of thesubject. The exposure of the camera is controlled by an output signalfrom the photometric sensor.

According to a further aspect of the present invention, a first imagesensor which receives light from a subject and a second image sensorcapable of receiving light of the same image as the first image sensorand having a spectral sensitivity characteristic different from that ofthe first image sensor are provided in the image-processing device. Acolor-correcting coefficient is calculated by a color-correctingcoefficient determining part based on each output value obtained byphotoelectrical conversion in the first image sensor and the secondimage sensor. By using the calculated color-correcting coefficient, acolor-correcting part performs color correction on a synthesized outputvalue of the first image sensor and the second image sensor. By usingthe first and the second image sensors each having a different spectralsensitivity characteristic in this manner, parameters for receiving andrecognizing the light from a subject field can be easily increased toobtain a favorable color reproduction characteristic. In the case wherethe image-processing device is applied to a conventional electroniccamera including the first and the second image sensors, only a changein the signal-processing method is required. Therefore, the presentinvention can be easily applied to an existing electronic camera.Moreover, color correction is performed on the synthesized output valueof the first image sensor and the second image sensor by thecolor-correcting part. As a result, a signal of an image closer to thatperceived by the human eye can be multiplied by the color-correctingcoefficient.

BRIEF DESCRIPTION OF THE DRAWINGS

The nature, principle, and utility of the invention will become moreapparent from the following detailed description when read inconjunction with the accompanying drawings in which like parts aredesignated by identical reference numbers, in which:

FIG. 1 is an explanatory diagram showing an electronic camera includingan image-processing device according to a first embodiment of thepresent invention;

FIG. 2 is a block diagram showing a process of the image-processingdevice according to the first embodiment of the present invention;

FIG. 3 is an explanatory diagram showing spectral sensitivitycharacteristics of CCDs of the image-processing device according to thefirst embodiment of the present invention;

FIG. 4 is a flowchart showing a process in a color-correctingcoefficient generating unit shown in FIG. 2;

FIG. 5 is an explanatory diagram showing an LUT in the embodiments ofthe image-processing device of the present invention;

FIG. 6 is an explanatory diagram showing a color-correcting coefficientselecting table in the embodiments of the image-processing device of thepresent invention;

FIG. 7 is a block diagram showing a process of the image-processingdevice according to a second embodiment of the present invention;

FIG. 8 is an explanatory diagram showing an electronic camera includingthe image-processing device according to a third embodiment of thepresent invention;

FIG. 9 is a block diagram showing a process of the image-processingdevice according to the third embodiment of the present invention;

FIG. 10 is an explanatory diagram showing spectral sensitivitycharacteristics of CCDs of the image-processing device according to thethird embodiment of the present invention; and

FIG. 11 is a flowchart showing a process in a color-correctingcoefficient generating unit shown in FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

First Embodiment

FIG. 1 is an explanatory diagram showing an electronic camera includingan image-processing device according to a first embodiment of thepresent invention.

An electronic camera 2 includes: an external flash device 1 forilluminating a subject with light; and a camera body unit 3 capable ofcontrolling the external flash device 1.

The external flash device 1 includes: a xenon tube 5 for converting acurrent energy into a luminous energy; a light-emission controlling unit7 for controlling a photocurrent in the xenon tube 5 to cause flat lightemission. The external flash device 1 also includes a reflector 9 and aFresnel lens 11 for efficiently radiating a light beam emitted from thexenon tube 5 onto the subject. The external flash device 1 furtherincludes: a sensor 13 for monitoring; and a glass fiber 15 forconnecting the sensor 13 and the reflector 9 with each other so as todirect the light beam emitted from the xenon tube 5 to the sensor 13.

The camera body unit 3 includes: a photo-taking lens unit 17; and a bodyunit 19 to which the photo-taking lens unit 17 is attached.

The photo-taking lens unit 17 includes a photo-taking lens 21 forcollecting the light beam from the subject and a diaphragm 22.

The body unit 19 includes a half mirror 23 which pivots between aposition where the half mirror 23 can receive the light beam transmittedthrough the photo-taking lens 21 (hereinafter, referred to as a closedstate) and a position where the half mirror 23 cannot receive the lightbeam (hereinafter, referred to as an opened state). A film 25 made ofsilver halide salt is attached to the main body unit 19. The film 25 canreceive the light beam transmitted through the photo-taking lens 21among light emitted from the external flash device 1 and then reflectedby the subject. The body unit 19 includes a shutter 27 for selectivelyshielding light in front of the film 25.

The body unit 19 also includes: a CCD 29 serving as a first image sensorprovided so as to be capable of receiving the light beam reflected bythe shutter 27 or the film 25 among the light beams transmitted throughthe photo-taking lens 21; and an electric circuit 31 for controlling theexternal flash device 1 based on the photometric results of the CCD 29.

The body unit 19 further includes a focusing glass 33 provided at animaging position of the photo-taking lens 21 through the half mirror 23when the half mirror 23 is in a closed state. The body unit 19 alsoincludes: a displaceable penta prism 35 for changing a light path of thelight beam transmitted through the focusing glass 33; and a finder 37 toobserve the light beam from the penta prism 35. The body unit 19 furtherincludes: a collective lens 39 for collecting the light transmittedthrough the penta prism 35 when the penta prism 35 is situated at adifferent position from an incident position of the light reflected fromthe penta prism 35 on the finder 37; and a CCD 41 serving as a secondimage sensor for receiving the light transmitted through the collectivelens 39. The CCD 41 is used as a calorimetric sensor.

A contact 43 is provided as an interface between the external flashdevice 1 and the camera body unit 3.

Next, an optical system of the electronic camera 2 having theabove-described structure will be described.

When the subject is to be observed through the finder 37, a part of thelight beam transmitted through the photo-taking lens 21 is reflected bythe half mirror 23 in the closed state indicated with a broken line.Then, the reflected light beam transmits through the focusing glass 33and the penta prism 35 so as to be directed to the finder 37.

When a release button (not shown) is pressed down for photographing, thehalf mirror 23 is moved to a position of the opened state indicated witha solid line so as to lower the aperture of the diaphragm 22 and to openthe shutter 27. Nearly simultaneously, the xenon tube 5 makes a realflash to illuminate the subject. The light reflected from the subjectreaches the film 25 through the photo-taking lens 21. The light beamreflected by the film 25 enters the CCD 29.

Next, FIG. 2 is a block diagram showing the image-processing deviceaccording to the first embodiment of the present invention.

An image-processing device 45 includes: the CCD 29 for receiving thelight from the subject; and the CCD 41 capable of receiving the light ofthe same image as the CCD 29 and having a spectral sensitivitycharacteristic different from that of the CCD 29. The CCD 29 and the CCD41 have different spectral sensitivity characteristics from each otheras shown in FIG. 3. Their spectral sensitivity characteristics are madecloser to that of the human eye by increasing parameters. Moreover,color filters of R, G, and B having the same light transmittance areprovided for the CCD 29 and the CCD 41.

An output of the CCD 29 is subjected to A/D conversion or correction ofa variation in power source voltage caused by a change in temperatureand the like, in a signal-processing unit 47. Then, an output of thesignal-processing unit 47 is input to a white balance unit 49 and anevaluation value generating unit 59.

In the white balance unit 49, image signals are multiplied respectivelyby white balance gains Kr and Kb so as to prevent any change fromoccurring in an output image due to a difference in colorcharacteristics of a light source for illuminating the subject. Morespecifically, the following process is performed:R′=Kr×RG′=GB′=Kb×B.

R, G, B: image signals before white balance correction

R′, G′, B′: image signals after white balance correction

An output of the white balance unit 49 is input to an interpolation unit51. In the interpolation unit 51, a color interpolation process isperformed by a pixel local operation so as to perform correction on allthe pixels. More specifically, a color of an arbitrary pixel isestimated from the pixels in the vicinity of the arbitrary pixel.

On the other hand, in the evaluation value generating unit 59, an imageis divided into small areas, for example, in 8 rows and 12 columns.Then, evaluation values such as a luminance value or a chromaticityvalue are calculated for each of the small areas. The luminance is inproportion to absolute luminosity of a color of an object. Thechromaticity corresponds to an objectively measured color of the object,which excludes the luminance information.

In this first embodiment, in a color-correcting coefficient generatingunit 61 corresponding to a color-correcting coefficient determiningpart, a color-correcting coefficient is calculated based on the outputsof the CCD 41 and the evaluation value generating unit 59.

Hereinafter, a method of calculating the color-correcting coefficientwill be specifically described with reference to a flowchart in FIG. 4.

At step S11, coordinate transformation for making the coordinatedimensionless is performed.

More specifically, integrated values of output values from each of thesmall areas of the image from the CCD 29 for the respective primarycolors are referred to as Rs, Gs, and Bs, respectively. In a similarmanner, the CCD 41 is also divided into small areas, for example, in 8rows and 12 columns. Integrated values for each of the small areas forthe respective colors are referred to as Rm, Gm, and Bm, respectively.Then, an operation as follows is performed:RGs=Rs/GsBGs=Bs/GsRGm=Rm/GmBGm=Bm/Gm.

RGs, BGs, RGm, BGm: first false color-correcting coefficients

At step S12, normalization is performed using the first falsecolor-correcting coefficients RGs, BGs, RGm, and BGm and coefficients ina coefficient table unit 63. Specifically, an operation as follows isperformed:RGs′=RGs×k1+k2BGs′=BGs×k1+k2RGm′=RGm×k3+k4BGm′=BGm×k3+k4.

k1, k2, k3, k4: coefficients

RGs′, BGs′, RGm′, BGm′: second false color-correcting coefficients

At step S13, color-correcting coefficients are calculated with referenceto an LUT based on the second false color-correcting coefficients RGs′,BGs′, RGm′, and BGm′.

More specifically, a coefficient number is obtained with reference tothe LUT shown in FIG. 5 based on the second false color-correctingcoefficients RGs′, BGs′, RGm′, and BGm′.

Subsequently, color-correcting coefficients CC0 to CC8 corresponding tothe coefficient number selected from FIG. 5 are selected with referenceto a table shown in FIG. 6. In the above-described manner, thecalculation of the color-correcting coefficients is terminated.

The coefficient numbers are listed in a longitudinal direction of thetable shown in FIG. 5, whereas the second false color-correctingcoefficients RGs′, BGs′, RGm′, and BGm′ are listed in a horizontaldirection.

The coefficient numbers are listed in a longitudinal direction of thetable shown in FIG. 6, whereas the color-correcting coefficients CC0 toCC8 are listed in a horizontal direction.

In a coefficient interpolation unit 65, coefficient interpolation isperformed so as to reduce a step generated by a difference in thecolor-correcting coefficients CC0 to CC8 calculated by thecolor-correcting coefficient generating unit 61 at the respectiveboundaries between the small areas. The coefficient interpolation isperformed by linear interpolation using the coefficients of the smallareas in the vicinity. Color-correcting coefficients after thecoefficient interpolation are hereinafter referred to as CC′0 to CC′8.

In a color-correcting unit 53 corresponding to a color-correcting part,a color-correcting operation as follows is performed by using imagesignals R″, G″, and B″ output from the interpolation unit 51 and thecolor-correcting coefficients CC′0 to CC′8 calculated in the coefficientinterpolation unit 65.R′″=R″×CC′0+G″×CC′1+B″×CC′2G′″=R″×CC′3+G″×CC′4+B″×CC′5B′″=R″×CC′6+G″×CC′7+B″×CC′8

In a γ-correction unit 55, a γ-characteristic is corrected. Theγ-characteristic is appropriately selected in accordance with contrastof the subject. More specifically, the γ-characteristic is calculatedbased on the luminance value calculated in the evaluation valuegenerating unit 59.

In an edge enhancing unit 57, a process for enhancing an edge of theimage is performed.

In the first embodiment, the CCDs 29 and 41 each having a differentspectral sensitivity characteristic are provided so as to increase theparameters when the CCDs 29 and 41 receive and recognize light from asubject field. Therefore, the spectral sensitivity characteristic can bemade closer to that of the human eye so as to obtain a favorable colorreproduction characteristic. Furthermore, in the case where the firstembodiment of the present invention is applied to a conventionalelectronic camera having the CCDS 29 and 41, a change in thesignal-processing method is only required. Accordingly, the firstembodiment can be easily applied to an existing electronic camera.

Moreover, in the first embodiment, the CCD 29 and the CCD 41 use adifferent number of pixels to receive the light from the same subject.Since the observation of the subject is achieved with the two CCDs 29and 41, the image can be prevented from being coarse even when thenumber of pixels used by any one of the CCDs 29 and 41 is reduced.Therefore, the amount of time required for the image processing can bereduced.

Furthermore, in the first embodiment, the CCD 29 is divided into theplurality of small areas. Then, the CCD 41 is also divided into theplurality of small areas so as to correspond to the small areas of theCCD 29. An output value of each of the pixels of the CCD 29 and the CCD41 is integrated for each of the small areas so that the integratedvalues are used to calculate the color-correcting coefficients.Accordingly, as compared with the case where the color-correctingcoefficients are calculated for each pixel, it is ensured that theamount of time required for the image processing can be reduced.

Second Embodiment

FIG. 7 is a block diagram showing an image-processing device accordingto a second embodiment of the present invention. The second embodimentdiffers from the first embodiment only in the signal-processing method.

The same parts as those of the first embodiment will be designated byidentical reference numbers in the second embodiment, and detaileddescription thereof will be omitted.

An image-processing device 67 includes the CCDs 29 and 41, each havingcolor filters of R, G, and B for receiving light from a subject.

The outputs of the CCDs 29 and 41 are subjected to A/D conversion orcorrection of a variation in power source voltage caused by a change intemperature and the like, in the signal-processing units 47 and 47A,respectively. Then, outputs of the signal-processing units 47 and 47Aare input to a signal synthesis unit 69 and the evaluation valuegenerating units 59 and 59A, respectively.

In the signal synthesis unit 69, two signals are synthesized to generatea signal of an image closer to that perceived by the human eye.Subsequently, an output of the signal synthesis unit 69 is input throughthe white balance unit 49 and the interpolation unit 51 to thecolor-correcting unit 53.

On the other hand, in each of the evaluation value generating units 59and 59A, an image is divided into small areas, for example, in 8 rowsand 12 columns. Then, an evaluation value such as a luminance value or achromaticity value is calculated for each of the small areas.

In the color-correcting coefficient generating unit 61, acolor-correcting coefficient is calculated based on the outputs of theevaluation value generating units 59 and 59A and the coefficient tableunit 63.

In the coefficient interpolation unit 65, coefficient interpolation isperformed so as to reduce a step at the respective boundaries betweenthe small areas due to a difference in the color-correcting coefficientsCC0 to CC8 calculated by the color-correcting coefficient generatingunit 61. Then, the color-correcting coefficients CC′0 to CC′8 arecalculated.

In the color-correcting unit 53, a color-correcting operation isperformed by using image signals output from the interpolation unit 51and the color-correcting coefficients CC′0 to CC′8 calculated in thecoefficient interpolation unit 65. Subsequently, an output of thecolor-correcting unit 53 is sequentially transmitted to the γ-correctionunit 55 and the edge enhancing unit 57.

The image-processing device 67 can also achieve the same effects asthose of the first embodiment.

In the image-processing device of the second embodiment as describedabove, a synthesized output value of the CCD 29 and the CCD 41 eachhaving a different spectral sensitivity characteristic is subjected tocolor conversion in the color-correcting unit 53. Therefore, it ispossible to multiply a signal of an image closer to that perceived bythe human eye by the color-correcting coefficient as compared with thecase where the output signal of one of the CCDs, i.e., the CCD 29, ismultiplied by the color-correcting coefficient as in the firstembodiment.

Third Embodiment

FIG. 8 is an explanatory view showing an electronic camera including animage-processing device according to a third embodiment of the presentinvention.

The same parts as those of the first embodiment will be designated byidentical reference numbers in the third embodiment, and detaileddescription thereof will be omitted.

An electronic camera 2A includes the photo-taking lens unit 17 and thebody unit 19 to which the photo-taking lens unit 17 is attached.

The photo-taking lens unit 17 includes the photo-taking lens 21 forcollecting the light beam from the subject and the diaphragm 22.

The body unit 19 includes a mirror 23A which pivots between a positionwhere the mirror 23A can receive the light beam transmitted through thephoto-taking lens 21 (hereinafter, referred to as a closed state) and aposition where the mirror 23A cannot receive the light beam(hereinafter, referred to as an opened state).

The body unit 19 also includes a CCD 29A serving as a first image sensorcapable of receiving the light beam transmitted through the photo-takinglens 21. The CCD 29A captures an image of the subject. The shutter 27 isprovided in front of the CCD 29A.

The body unit 19 further includes the focusing glass 33 provided at animaging position of the photo-taking lens 21 through the mirror 23A whenthe mirror 23A is in a closed state. The body unit 19 also includes: thepenta prism 35 for changing a light path of the light beam transmittedthrough the focusing glass 33; and the finder 37 serving to observe thelight beam from the penta prism 35.

The body unit 19 further includes: the collective lens 39 for collectingthe light transmitted through the penta prism 35; and the CCD 41 servingas a second image sensor for receiving the light transmitted through thecollective lens 39. The CCD 41 is used as a colorimetric sensor. Theexposure is controlled by a colorimetric signal from the CCD 41.

An optical system of the electronic camera 2A having the above-describedstructure will now be described.

When the subject is to be observed through the finder 37, a part of thelight beam transmitted through the photo-taking lens 21 is reflected bythe mirror 23A in the closed state indicated with a broken line in FIG.8. Then, the reflected light beam transmits through the focusing glass33 and the penta prism 35 so as to be directed to the finder 37.

When a release button (not shown) is pressed down for photographing, themirror 23A is moved to a position of the opened state indicated with asolid line so as to lower the aperture of the diaphragm 22 and to openthe shutter 27. The light from the subject transmitted through thephoto-taking lens 21 forms an image on the CCD 29A so as to performimage capture.

Next, FIG. 9 is a block diagram showing an image-processing deviceaccording to the third embodiment of the present invention.

An image-processing device 45A includes: the CCD 29A for receiving thelight from the subject; and the CCD 41 capable of receiving the light ofthe same image as the CCD 29 and having a spectral sensitivitycharacteristic different from that of the CCD 29A. The CCD 29A and theCCD 41 have different spectral sensitivity characteristics from eachother as shown in FIG. 10. Color filters of R, G, and B having the samelight transmittance are provided for the CCD 29A and the CCD 41.

An output of the CCD 29A is output to the signal-processing unit 47where the output is subjected to A/D conversion, clamping, sensitivitycorrection, and the like. Subsequently, an output of thesignal-processing unit 47 is input to the white balance unit 49 and theevaluation value generating unit 59.

In the white balance unit 49, image signals are multiplied respectivelyby white balance gains. Kr and Kb so as to prevent any change fromoccurring in an output image due to a difference in colorcharacteristics of a light source for illuminating the subject.

More specifically, the following process is performed:R′=Kr×RG′=GB′=Kb×B.

R, G, B: image signals before white balance correction

R′, G′, B′: image signals after white balance correction

An output of the white balance unit 49 is input to the interpolationunit 51. In the interpolation unit 51, a color interpolation process isperformed by a pixel local operation so as to perform correction on allthe pixels. More specifically, a color of an arbitrary pixel isestimated from the pixels in the vicinity of the arbitrary pixel.

On the other hand, in the evaluation value generating unit 59, an imageis divided into small areas, for example, in 8 rows and 12 columns.Then, an evaluation value such as a luminance value or a chromaticityvalue is calculated for each of the small areas. The luminance is inproportion to absolute luminosity of a color of an object. Thechromaticity corresponds to an objectively measured color of the object,which excludes the luminance information.

In this third embodiment, in the color-correcting coefficient generatingunit 61 corresponding to a color-correcting coefficient determiningpart, a color-correcting coefficient is calculated based on the outputsof the CCD 41 and the evaluation value generating unit 59. After beingsubjected to A/D conversion, clamping, sensitivity correction, and thelike in the signal-processing unit 47A, the output of the CCD 41 isoutput to the color-correcting coefficient generating unit 61.

Hereinafter, a method of calculating the color-correcting coefficientwill be specifically described with reference to a flowchart in FIG. 11.

At step S11, coordinate transformation for making the coordinatedimensionless is performed.

More specifically, integrated values of the respective primary colors ofan output value from each of the small areas of the image from the CCD29A are referred to as Rs, Gs, and Bs, respectively. In a similarmanner, the CCD 41 is divided into small areas, for example, in 8 rowsand 12 columns, and integrated values of the respective primary colorsfor each of the small areas are referred to as Rm, Gm, and Bm,respectively. Then, an operation as follows is performed:RGs=Rs/GsBGs=Bs/GsRGm=Rm/GmBGm=Bm/Gm.

RGs, BGs, RGm, BGm: first false color-correcting coefficients

At step S12, normalization is performed using the first falsecolor-correcting coefficients RGs, BGs, RGm, and BGm and coefficients inthe coefficient table unit 63. Specifically, an operation as follows isperformed:RGs′=RGs×k1+k2BGs′=BGs×k1+k2RGm′=RGm×k3+k4BGm′=BGm×k3+k4.

k1, k2, k3, k4: coefficients

RGs′, BGs′, RGm′, BGm′: second false color-correcting coefficients

At step S13, a color-correcting coefficient is calculated with referenceto the LUT based on the second false color-correcting coefficients RGs′,BGs′, RGm′, and BGm′.

More specifically, a coefficient number is obtained with reference tothe LUT shown in FIG. 5 based on the second false color-correctingcoefficients RGs′, BGs′, RGm′, and BGm′. Subsequently, color-correctingcoefficients CC0 to CC8 corresponding to the coefficient number selectedfrom FIG. 5 are selected with reference to a table shown in FIG. 6.

In the above-described manner, the calculation of the color-correctingcoefficients is terminated.

In the coefficient interpolation unit 65, coefficient interpolation isperformed so as to reduce a step at the respective boundaries betweenthe small areas due to a difference in the color-correcting coefficientsCC0 to CC8 calculated by the color-correcting coefficient generatingunit 61. The coefficient interpolation is performed by linearinterpolation using the coefficients of the small areas in the vicinity.Color-correcting coefficients after the coefficient interpolation arehereinafter referred to as CC′0 to CC′8.

In the color-correcting unit 53 corresponding to a color-correctingpart, a color-correcting operation as follows is performed by usingimage signals R″, G″, and B″ output from the interpolation unit 51 andthe color-correcting coefficients CC′0 to CC′8 calculated in thecoefficient interpolation unit 65.R′″=R″×CC′0+G″×CC′1+B″×CC′2G′″=R″×CC′3+G″×CC′4+B″×CC′5B′″=R″×CC′6+G″×CC′7+B″×CC′8

Subsequently, image signals R′″, G′″, and B′″, which are subjected tocolor correction in the color-correcting unit 53, sequentially undergoprocesses in the γ-correction unit 55, a color space transformation unit56, and the edge enhancing unit 57 so as to be recorded onto a recordingmedium.

In the third embodiment, the CCDs 29A and 41 each having a differentspectral sensitivity characteristic are provided so as to increase theparameters when the CCDs 29A and 41 receive and recognize light from asubject field. Therefore, the spectral sensitivity characteristic can bemade closer to that of the human eye so as to obtain a favorable colorreproduction characteristic. Furthermore, in the case where the thirdembodiment of the present invention is applied to a conventionalelectronic camera including the CCDs 29A and 41, a change in thesignal-processing method is only required. Accordingly, the thirdembodiment of the present invention can be easily applied to an existingelectronic camera.

Furthermore, in the third embodiment, the CCD 29A is divided into theplurality of small areas. Then, the CCD 41 is also divided into theplurality of small areas so as to correspond to the small areas of theCCD 29A. An output value of each of the pixels of the CCD 29A and theCCD 41 is integrated for each of the small areas so that thecolor-correcting coefficients are calculated by using the integratedvalues. Accordingly, even when the CCDs 29A and 41 have a differentnumber of pixels, it is ensured that a favorable color reproductioncharacteristic can be easily obtained.

In the above-described embodiments, the CCD 41 is used as a colorimetricsensor. However, the CCD 41 may also be used as a photometric sensor formeasuring the luminance of a subject.

In the above-described embodiments, a functional operation using thecoefficients k1 to k4 is performed for normalization in thecolor-correcting coefficient generating unit 61. However, aone-dimensional LUT or a multidimensional LUT may be used instead.

Furthermore, in the above-described embodiments, the color-correctingcoefficients CC0 to CC8 are selected so as to perform a 3-by-3 matrixoperation. However, in order to perform color correction with higheraccuracy, a multidimensional LUT may be selected to perform anoperation, for example.

The invention is not limited to the above embodiments and variousmodifications may be made without departing from the spirit and scope ofthe invention. Any improvement may be made in part or all of thecomponents.

1. An image-processing device comprising: a first image sensor whichreceives light from a subject and outputs a first plurality of colorcomponents; a second image sensor, whose spectral sensitivitycharacteristic of a second plurality of color components differs fromthat of said first image sensor, which receives light of the same imageas said first image sensor and is capable of outputting the secondplurality of color components; a color-correcting coefficientdetermining part which calculates a color-correcting coefficientaccording to a status of light received from the subject, based on eachoutput value obtained by photoelectrical conversion in said first imagesensor and said second image sensor; and a color-correcting part whichperforms color correction on the output value of said first image sensorby using said color-correcting coefficient calculated by saidcolor-correcting coefficient determining part.
 2. The image-processingdevice according to claim 1, wherein: said first image sensor is dividedinto a plurality of small areas, and said second image sensor is dividedinto a plurality of small areas so as to correspond to the plurality ofsmall areas of said first image sensor; and the output value of eachpixel of said first image sensor and said second image sensor isintegrated for each of said small areas so as to calculate saidcolor-correcting coefficient by using the integrated value.
 3. Theimage-processing device according to claim 2, wherein said first imagesensor and said second image sensor use a different number of pixels toreceive the light from the same subject.
 4. The image-processing deviceaccording to claim 1, wherein said second image sensor is used as acolorimetric sensor which measures color balance of said subject.
 5. Theimage-processing device according to claim 1, wherein said second imagesensor is used as a photometric sensor which measures luminance of saidsubject.
 6. An image-processing device comprising: a first image sensorwhich receives light from a subject and outputs a first plurality ofcolor components; a second image sensor, whose spectral sensitivitycharacteristic of a second plurality of color components differs fromthat of said first image sensor, receives light of the same image assaid first image sensor and is capable of outputting the secondplurality of color components; a color-correcting coefficientdetermining part which calculates a color-correcting coefficient basedon each output value obtained by photoelectrical conversion in saidfirst image sensor and said second image sensor; and a color-correctingpart which performs color correction on a synthesized output value ofsaid first image sensor and said second image sensor by using saidcolor-correcting coefficient calculated by said color-correctingcoefficient determining part.
 7. The image-processing device accordingto claim 6, wherein: said first image sensor is divided into a pluralityof small areas, and said second image sensor is divided into a pluralityof small areas so as to correspond to the plurality of small areas ofsaid first image sensor; and the output value of each pixel of saidfirst image sensor and said second image sensor is integrated for eachof said small areas so as to calculate said color-correcting coefficientby using the integrated value.
 8. The image-processing device accordingto claim 7, wherein said first image sensor and said second image sensoruse a different number of pixels to receive the light from the samesubject.
 9. The image-processing device according to claim 6, whereinsaid second image sensor is used as a colorimetric sensor which measurescolor balance of said subject.
 10. The image-processing device accordingto claim 6, wherein said second image sensor is used as a photometricsensor which measures luminance of said subject.